4.2.6. Exceptions to Market Value Standard.These Standards direct appraisers to estimate a property’s market value—not the just compensation due for a government acquisition269— because appraisers do not have the authority to determine just compensation under the Fifth Amendment.270 Rarely, deviation from market value as the measure of just compensation may be required in federal acquisitions, but “only ‘when market value has been too difficult to find, or when its application would result in manifest injustice to owner or public.’”271 Such situations are highly unusual,272 and moreover, inevitably require appropriate legal instruction.273 Whether departure from the established market value standard is appropriate in a given set of facts is a legal question beyond the scope of an appraiser to determine.274